Look-up table on film

ABSTRACT

A color look-up table includes a plurality of images recorded on a film. Each of the images being recorded on a separate picture of the film and containing at least a first level and a second level. The first and second levels having different pixel color values and are arranged to form a detectable geometric pattern on each of the pictures. The first field and a second field having detectable boundaries assigned to characterize distortions on the film.

FIELD OF THE INVENTION

The present invention relates to a method for recording a color look-uptable on film wherein at least two levels are recorded on each pictureof the film, and the levels are recorded such that a detectablegeometric pattern is formed. The invention further relates to a methodof recording and using the same.

BACKGROUND OF THE INVENTION

In order to be able to restore colors in pictures of a film, a colorlook-up table is recorded on the film. The color look-up table istypically recorded on the film, for example, in 21 levels. The value ofeach level is recorded on a picture of the film. After the pictures thatcontain the color look-up table are scanned, a scanner, computer, orother devices restore the colors of the pictures in the film based onthe color look-up table.

The above-described color look-up table, however, has the drawback thatwhen a film is in need of restoration, 21 levels do not providesufficient resolution to accurately restore the film. Increasing theamount of levels recorded on the film, however, directly increases theamount of space needed on the film to record the color look-up table.Additionally, there is no current method to correct geometricdistortions in the film due to film degradation.

It is therefore desirable to provide a color look-up table that canprovide sufficient resolution to accurately restore the film withouttaking-up excessive space on the film. It is further desirable toprovide a color look-up table that enables geometric distortion due tofilm degradation to be detected and corrected.

SUMMARY OF THE INVENTION

The invention provides a film capable of correcting physical distortioncomprising at least one of image recorded on a film, each of the atleast one images being recorded on a separate picture of the film andcontaining at least a first field or level and a second field or levelhaving detectable boundaries. The at least one images can be a colorlook-up table, wherein the first and second levels having differentpixel color values.

An embodiment of the invention is a method that includes the steps ofproviding on film one or more images of a geometric pattern, scanningthe images, detecting distortions of the geometric pattern of theimages, generating instructions for correcting distortions in thegeometric pattern and applying corrections to other images on the film.The method can further comprise building a color look-up table in theimages and performing color corrections on the film, wherein the colorlook-up table on the images contain at least a first color level and asecond color level and selecting the first and second color levels tohave different values. The first and second color levels can be shapedto form a detectable geometric pattern on each of the images. Thegenerating instructions step can comprise generating an affinetransformation to correct deviations in the geometric pattern and theapplying corrections step can comprise applying the affinetransformation to the other images.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings.

FIG. 1 is a schematic illustration of a color look-up table provided ona reel of film according to the invention.

FIG. 2 is a schematic illustration of an image recorded on the colorlook-up table of FIG. 1.

FIG. 3 is a schematic illustration of a first image recorded on thecolor look-up table of FIG. 1.

FIG. 4 is a flow chart showing a method of use of the color look-uptable of FIG.

1.

FIG. 5 is an image having distortions prior to correction.

FIG. 6 is the image of FIG. 5 after correction according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a color look-up table 1 according to the invention. Asshown in FIG. 1, the color look-up table 1 comprises a series of images2 (or steps) formed over a plurality of pictures 3 (or frames) on a film4. The color look-up table 1 may be formed, for example, over aplurality of the pictures 3 at a beginning of a reel of the film 4. Thecolor look-up table 1 contains representative pixel information that maybe used for restoring colors in the film 4. The color look-up table 1corresponds to one color component on the film 4, for example, red,green, or blue.

The color look-up table 1 in the film 4 may have 8-bits, 10 bits, 12bits, or 16 bits to represent a pixel. As shown in Table 1, which isillustrated below, if the film 4 uses 8 bits to represent a pixel, thenthe color look-up table 1 may have 256 possible pixel color values(which can be referred to as color values, levels or intensities). Table1 can be the color look-up table for red, green, or blue. (In otherwords each color has its own look-up table.) If the film 4 uses 10 bitsto represent a pixel, then the color look-up table 1 may have 1024possible pixel color values. It will be appreciated by those skilled inthe art, however, that the number of bits used to represent a pixel mayvary depending on the desired application of the color look-up table 1.

TABLE 1 True Intensity vs. Level Recorded Level L_(n) 0 1 2 3 4 5 6 7 89 10 11 12 13 14  8-bits 0 4 8 12 16 20 24 28 32 36 40 44 48 52 5610-bits 0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 Level L_(n)15 16 17 18 19 20 21 22 23 24 25 26 27 28 29  8-bits 60 64 68 72 76 8084 88 92 96 100 104 108 112 116 10-bits 240 256 272 288 304 320 336 352368 384 400 416 432 448 464 Level L_(n) 30 31 32 33 34 35 36 37 38 39 4041 42 43 44  8-bits 120 124 128 132 136 140 144 148 152 156 160 164 168172 176 10-bits 480 496 512 528 544 560 576 592 608 624 640 656 672 688704 Level L_(n) 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59  8-bits 180184 188 192 196 200 204 208 212 216 220 224 228 232 236 10-bits 720 736452 468 784 800 816 832 848 864 880 896 912 928 944 Level L_(n) 60 61 6263 64  8-bits 240 244 248 252 256 10-bits 960 976 992 1008 1024

The pixel color values are recorded on the film 4 in levels. The morelevels that are recorded on the film 4, the greater the resolution ofthe images reproduced. In Table 1, 65 levels (0-64) are recorded on thefilm 4. It will be appreciated by those skilled in the art, however,that the number of levels recorded on the film 4 may vary depending onthe desired image and the amount of available storage space.

The configuration of the color look-up table 1 will now be described ingreater detail. As shown in FIG. 1, the color look-up table 1 comprisesthe images 2. As shown in FIG. 2, each of the images 2 contains a firstlevel 5 (or a first intensity level 5) and a second level 6 (or a secondintensity level 6). In the illustrated embodiment, the first level 5 isrepresented by the formula (L_(n)), and the second level 6 isrepresented by the formula (L_(n+32)). The value of n increases witheach of the images 2 and is determined by the number of levels that areto be recorded on the film 4. For example, in the illustratedembodiment, the value of n increases with each of the images 2 from0-32, because 65 levels are recorded on the film 4. The first and secondlevels 5, 6 are substantially recorded in columns 12 and rows 13. Thefirst and second levels 5, 6 substantially alternate along the columns12 and the rows 13 such that the first level 5 is positioned next to thesecond level 6.

Although the images 2 are shown and described herein as each having beenrecorded with only two of the levels, it will be appreciated by thoseskilled in the art that either a single level or more than two of thelevels may be recorded on each of the images 2 depending on the desiredimage and the amount of available storage space. Additionally, althoughthe levels are shown and described herein as being formed in fourcolumns and four rows, it will be appreciated by those skilled in theart that the levels may be formed in any number of columns and/or therows depending on the desired image and the amount of available storagespace.

A feature of the invention is that the images 2 containing the first andsecond levels 5, 6 on the pictures 3, form detectable geometric patternson each of the pictures 3. (Detectable geometric pattern means that eachlevel 5, 6 is a field having a defined boundary that can bemathematically characterized.) For example, an outer edge of the firstand second levels 5, 6 defines a perimeter 7 of the image 2 on thepicture 3. Additionally, the color differences between the first andsecond levels 5, 6 as the first and second levels 5, 6 alternate alongthe columns 12 and the rows 13 define a plurality of intersecting firstcross-bars 10 and second cross-bars 11. In the illustrated embodiment,the first cross-bars 10 extend substantially parallel to each other, andthe second cross-bars 11 extend substantially parallel to each other.The first and second cross-bars 10, 11 intersect at an angle of about 90degrees. The first and second cross-bars 10, 11 intersect the perimeter7 at an angle of about 90 degrees.

A method for providing the color look-up table 1 on the film 4 will nowbe described in greater detail. As shown in FIG. 1, a first image 2 a isrecorded on a first picture 3 a of the film 4. As shown in FIG. 3, thefirst image 2 a (which can be a first frame on the film) contains thefirst level 5 and the second level 6. The first level 5 contains pixelcolor values corresponding to Level 0 (L₀), which is the lowest levelillustrated in Table 1. The second level 6 contains pixel color valuescorresponding to Level 32 (L₀₊₃₂ or L₃₂), which is the substantiallymiddle level illustrated in Table 1. The first and second levels 5, 6are recorded in the columns 12 and the rows 13 such that the first andsecond levels 5, 6 alternate along the columns 12 and the rows 13.

As shown in FIG. 1, a second image 2 b is recorded on a second picture 3b of the film 4. The second image 2 b contains the first levels 5 andthe second levels 6 too. The first level 5 contains pixel color valuescorresponding to Level 1 (L₁), which is one level above the lowest levelillustrated in Table 1. The second level 6 contains pixel color valuescorresponding to Level 33 (L₁₊₃₂ or L₃₃), which is one level above thesubstantially middle value illustrated in Table 1. The first and secondlevels 5, 6 are recorded in the columns 12 and the rows 13 such that thefirst and second levels 5, 6 alternate along the columns 12 and the rows13.

The images 2 are continued to be recorded on the film 4 until all 65levels are recorded on the film 4. In the illustrated embodiment, thecolor look-up table 1 can contain 33 of the images 2 wherein each of theimages 2 is a step and contains two of the levels shown in Table 1. Forexample, if the color values are based on 10 bit system, Level 0 (L₀)will have a true intensity value of 0 and Level 32 (L₀₊₃₂ or L₃₂) willhave a true intensity value of 512. The combination of Level 0 (L₀) andLevel 32 (L₀₊₃₂ or L₃₂) can comprise a step 1 or a 1^(st) frame on thecolor look-up table 1 of the film. Level 1 (L₁) will have a trueintensity value of 16 and Level 33 (L₁₊₃₂ or L₃₃) will have a trueintensity value of 528. The combination of Level 1 (L₁) and Level 33(L₁₊₃₂ or L₃₃) can comprise a step 2 or a 2^(nd) frame on the colorlook-up table 1 of the film. Level 31 (L₃₁) will have a true intensityvalue of 496 and Level 63 (L₃₁₊₃₂ or L₆₃) will have a true intensityvalue of 1008. The combination of Level 31 (L₃₁) and Level 63 (L₃₁₊₃₂ orL₆₃) can comprise a step 32 or a 32^(nd) frame on the color look-uptable 1 of the film. (Following a final step 33, the following frames orpictures of the film can contain the actual motion pictures images.) Anexample color look-up table 1 for a system with 65 levels according tothe invention is shown in Table 2. In this particular example Level L32appears twice (i.e., once in step 1 and again in step 33).

TABLE 2 Example Color Look-up Table Step No. in Color Table L(n) = LnL(n + 32) = Ln + 32 1 L(0) L(32) 2 L(1) L(33) 3 L(2) L(34) 4 L(3) L(35)5 L(4) L(36) 6 L(5) L(37) 7 L(6) L(38) 8 L(7) L(39) 9 L(8) L(40) 10 L(9)L(41) 11 L(10) L(42) 12 L(11) L(43) 13 L(12) L(44) 14 L(13) L(45) 15L(14) L(46) 16 L(15) L(47) 17 L(16) L(48) 18 L(17) L(49) 19 L(18) L(50)20 L(19) L(51) 21 L(20) L(52) 22 L(21) L(53) 23 L(22) L(54) 24 L(23)L(55) 25 L(24) L(56) 26 L(25) L(57) 27 L(26) L(58) 28 L(27) L(59) 29L(28) L(60) 30 L(29) L(61) 31 L(30) L(62) 32 L(31) L(63) 33 L(32) L(64)

It will be appreciated by those skilled in the art that the images 2 maybe recorded on the film 4 more than one time to ensure accuracy.Additionally, it will be appreciated by those skilled in the art thatthe images 2 may be recorded on the film 4 more than one time to recordmore than one color component on the film 4.

A feature of the invention is that the color look-up table is capable ofdetecting and correcting geometric distortion of the film. A method ofusing the color look-up table 1 will now be described with reference tothe flowchart 20 shown in FIG. 4. As shown in FIG. 4, at process step21, the entire film 4 including the color look-up table 1 is scanned bya conventional scanning method. At process step 22, as the color look-uptable 1 is scanned, a scanner, a computer, or other device detects thefirst and second levels 5, 6 on the pictures 3. At process step 23, ascanner, a computer, or other device builds a color look-up table on thescanner, computer, or other device. At process step 24, the scanner,computer, or other device makes color corrections in the pictures 3 ofthe film 4 based on the information retrieved from the color look-uptable 1 to restore the film 4, for example, to its original condition.Because the method of scanning the film 4 and making color correctionstherein are well known in the art, further description thereof has beenomitted.

At process step 25, as the color look-up table 1 is scanned, a scanner,a computer, or other device detects the geometric pattern formed on thepictures 3. For example, in the first picture 3 a shown in FIG. 3, theperimeter 7 and the first and second cross-bars 10, 11 of the firstimage 2 a are detected. At points where the first and second cross-bars10, 11 intersect, a substantially 90 degree angle should be detectedindicating that the first and second cross-bars 10, 11 are substantiallystraight lines. Additionally, at points where the first and secondcross-bars 10, 11 intersect the perimeter 7, a substantially 90 degreeangle should be detected indicating that the perimeter 7 is formed ofsubstantially straight lines. The detected position of the perimeter 7and the first and second cross-bars 10, 11 of the images 2 may berepresented by at least one equation.

At process step 26, if the perimeter 7 of the images 2 and/or the firstand second cross-bars 10, 11 of the images 2 are found not to besubstantially straight lines, then an affine transformation is generatedto correct deviations in the geometric pattern: At process step 27, theaffine transformation is applied to warp content in all of the pictures3 in the film 4 thereby correcting the geometry of all of the pictures 3in the film 4. Additionally, interpolation for color pixels not on theinteger grip may be made. As a result of this correction, any physicaldistortion appearing on the film 4 can be removed.

As shown in the flowchart 20, the detection of the first and secondlevels 5, 6 on the pictures 3 at process step 22 and the detection ofthe geometric pattern on the pictures 3 at process step 25 may occursimultaneously. The building of the color look-up table at process step23 and the generation of the affine transformation at process step 26may also occur simultaneously. Additionally, the color correction atprocess step 24 and the geometric correction of the content of thepictures 3 in the film 4 at process step 27 may be performedsimultaneously. It will be appreciated by those skilled in the art,however, that process steps 22, 23, and 24 may alternatively occureither before or after process steps 25, 26, and 27.

Although the color look-up table 1 shown and described herein is usedfor color correction and geometry restoration in the restoration of thefilm 4, it will be appreciated by those skilled in the art that thecolor look-up table 1 may be used for other purposes and in otherapplications. For example, the color look-up table 1 may be used invisible picture recording, printing for archiving, etc.

In the color look-up table 1 according to the invention, 65 levels arerecorded on the film 4, which enables the color look-up table 1 tosupport higher resolution images. Additionally, because two levels arerecorded in each of the images 2, the color look-up table 1 can becondensed into fewer of the pictures 3 on the film 4. Since the levelsalternate with respect to the columns 10 and the rows 11, the images 2are additionally provided with a geometric construction that enablesgeometric distortion to be detected and corrected.

An important point is that distortions of the frames or pictures of thefilm containing the color-look-up table 1 and the film having the actualmotion pictures images are likely to distort similarly. With thisconcept in mind, an approach for use of the invention will be described.An image 2 shown in FIG. 5, illustrates the film having distortionswhich can be visually observed because the borders between the firstlevels 5 and a second levels 6 are warped. FIG. 6 illustrates how theborders and the first levels 5 arid second levels 6 could ideally beshaped or how they may appear after correction. From FIG. 6, one cancompute coordinates of each vertex a to y by checking all edges. (Thecross point of two edges is a vertex.) The coordinates of each point is(a_(x), a_(y)), (b_(x), b_(y)), . . . (y_(x), y_(y)). One can then finda transform for each block. For example, block abgf could becharacterized as follows:

(a_(x), a_(y))˜(a′_(x), a′_(y)),

(b_(x), b_(y))˜(b′_(x), b′_(y)),

(g_(x), g_(y))˜(g′_(x), g′_(y)), and

(f_(x), f_(y))˜(f′_(x), f′_(y)).

The values of x′ and y′ can be described as follows:

y

x′=Ax+By+C

y′=Dx+Ey+F

A transform T for these equations can be written as

T=[A, B, C; D, E, F].

This leads to

A a _(x) +B a _(y) +C=a _(x)′

D a _(x) +E a _(y) +F=a _(y)′

A b _(x) +B b _(y) +C=b _(x)′

D b _(x) +E b _(y) +F=b _(y)′

A g _(x) +B g _(y) +C=g _(x)′

D g _(x) +E g _(y) +F=g _(y)′

A f _(x) +B f _(y) +C=f _(x)′

D f _(x) +E f _(y) +F=f _(y)′

With these 8 equations, one can find the 6-parameter affine transform Tand implement the transform to appropriately warp each point in theblock abgf to a′b′g′f′ and get the correct image geometry. The warpdetermined for these images 2 of the color look-up table can then beused to appropriately warp/shape pictures 3 (or frames) on a film 4having the motion picture images. With this methodology for correctingdistortion in mind, a feature of the invention is that the film has thecapability of correcting physical distortion characterized in that atleast one of image is recorded on a film; each of these images arerecorded on a separate picture of the film; and each of these imagescontains at least one first field (or level) 5′ and at least one secondfield (or level) 6′ having detectable boundaries, wherein the first andsecond fields do not necessarily have different pixel color values, butmay have some other distinguishable attribute (e.g. in texture,polarization, etc.). Essentially, the methodology for this feature ofthe invention is to use the process steps 21, 25, 26 and 27 described inFIG. 4. It is to be understood that there can be a plurality of firstfields and second fields in an image. (These images can be referred toas a look-up table.)

The foregoing illustrates some of the possibilities for practicing theinvention. Many other embodiments are possible within the scope andspirit of the invention. For example, although the color look-up table 1is illustrated as having two levels recorded in each of the images 2, itwill be appreciated by those skilled in the art that more than twolevels may be recorded in each of the images 2. Additionally, althoughthe color look-up table 1 is illustrated as having a total of 65 levels,it will be appreciated by those skilled in the art that the number oflevels may vary depending on the desired application of the colorlook-up table 1.

It is, therefore, intended that the foregoing description be regarded asillustrative rather than limiting, and that the scope of the inventionis given by the appended claims together with their full range ofequivalents.

1. A film comprising: at least one of image on film; each of the atleast one images being a separate image and containing at least a firstfield and a second field having detectable boundaries assigned tocharacterize distortions on the film; and, the at least one image is acolor look-up table.
 2. The film of claim 1, wherein the first field isa first color level and the second field is a second color level, thefirst and second color levels having different values.
 3. The film ofclaim 1, wherein an outer edge of the first and second levels define aperimeter of the image.
 4. The film of claim 3, wherein color valuedifferences between the first and second levels define first and secondcross-bars that intersect the perimeter.
 5. The film of claim 1, whereinthe first and second fields are arranged in columns and rows, the firstand second fields alternating along the columns and rows.
 6. The film ofclaim 1, wherein an outer edge of the first and second fields togetherdefine a perimeter of the image.
 7. The film of claim 6, wherein thefirst and second levels fields define first and second cross-bars thatintersect the perimeter.
 8. The film of claim 7, wherein the first andsecond fields are arranged in columns and rows, the first and secondfields alternating along the columns and rows.
 9. A method comprisingthe steps of: providing on film at least one image of a geometricpattern; scanning the at least one image; detecting distortions of thegeometric pattern of the at least one image; generating instructions forcorrecting distortions in the geometric pattern; and, applyingcorrections to other images on the film.
 10. The method of claim 9,wherein the providing step further comprises building a color look-uptable in the at least one image and performing color corrections on thefilm.
 11. The method of claim 10, wherein the providing step furthercomprises building the color look-up table on the at least one image tocontain at least a first color level and a second color level andselecting the first and second color levels to have different values.12. The method of claim 10, wherein the providing step further comprisesshaping the first and second color levels to form a detectable geometricpattern on each of the images.
 13. The method of claim 12, wherein theproviding step further comprises arranging the first and second colorlevels in columns and rows and having the first and second color levelsalternate along the columns and rows.
 14. The method of claim 9, whereinthe generating instructions step further comprises generating an affinetransformation to correct deviations in the geometric pattern.
 15. Themethod of claim 14, wherein the applying corrections step furthercomprises applying the affine transformation to other images.
 16. Themethod of claim 9, wherein the providing step further comprises buildingat least a first field and a second field having detectable boundariesin to the at least one image.
 17. The method of claim 16, wherein theproviding step further comprises arranging the first and second fieldsin columns and rows and having the first and second fields alternatingalong the columns and rows.
 18. The method of claim 17, wherein thegenerating instructions step further comprises generating an affinetransformation to correct deviations in the geometric pattern.
 19. Themethod of claim 18, wherein the applying corrections step furthercomprises applying the affine transformation to other images.